Failed/incomplete Return-To-Land after Landing Detection Issue

[VertLim]

Hi,

I experienced a safety critical issue with a x8 multirotor using the latest stable PX4 firmware (1.8.0). The issue is triggered by the already known landing detection issues (c.f. #9696) and leads to a non-completed return-to-land mode!

In case the "landed" state is entered and subsequently left again (although the copter is physically already on the ground), the copter "jumps" back in the air and hovers closely above ground. Afterwards, it will not land automatically any more! You can see in the log, that the vehicle_local_position_setpoint.vz (as well as vx and vy) is not "reset" to my landing speed of 1 m/s (MPC_LAND_SPEED). By contrast, it stays at 0 m/s, which causes the copter to hover just above the ground. This must not happen even with a poorly configured landing detector (e.g. MPC_THR_HOVER, etc.).

Clearly, this is a safety critical bug as the copter might never land when the RC is empty/broken.

Greetings,
Thomas

[feemi]

I have similar issue with octo coax wide configuration on 1.8.0. Vehicle landing states starts to change when i arm the vehicle. if it is in position mode, vehicle starts the ascend and moves vertically like bouncing.